High energy print hammer unit with fast settle out

ABSTRACT

A print hammer actuator comprises a main three-legged magnetic core having an operating winding on a middle or center leg, and an armature pivotally supported adjacent the lower leg with an extension at the other end providing a hammer face, and a projection opposite the middle leg which moves within the operating winding. A secondary magnetic core on the opposite side of the armature with a restore and damping winding operates to damp oscillations and improve settle-out.

United States Patent [191 Mako et a1.

[ June 26, 1973 1 HIGH ENERGY PRINT HAMMER UNIT WITH FAST SETTLE-OUT [75] Inventors: John Mako, Vestal; Joseph E.

Wallace, Endicott, both of N.Y.

[73] Assignee: International Business Machines Corporation, Armonk, N.Y.

22 Filed: June25, 1971 21 Appl. No.: 156,779

[52] U.S. Cl. 101/93, 355/277 [51] Int. Cl B41j 9/10 [58] Field of Search 335/266, 268, 267, 335/256, 257, 271, 277, 276; 101/93 C, 297, 287

[56] References Cited UNITED STATES PATENTS 3,072,045 1/1963 Goin 101/93 C 3,188,947 6/1965 Paige 101/93 C 3,195,453 7/1965 Thiemamy 101/93 C 3,233,540 2/1966 Grottrup 101/93 C Cunningham 101/93 C 3,335,659 8/1967 Schacht et a1. 101/93 C 3,354,818 11/1967 Haas 101/93 C 3,381,611 5/1968 Foley l0l/ll1 X 3,426,675 2/1969 Dalton 101/93 C 3,468,246 9/1969 Lee et a1. 101/93 C 3,543,906 12/1970 l-lladky 101/93 C Primary Examiner-William B. Penn AttorneyFrancis V. Giolma et a1.

[57] ABSTRACT A print hammer actuator comprises a main threelegged magnetic core having an operating winding on a middle or center leg, and an armature pivotally supported adjacent the lower leg with an extension at the other end providing a hammer face, and a projection oppositethe middle leg which moves within the operating winding. A secondary magnetic core on the opposite side of the armature with a restore and damping winding operates to damp oscillations and improve settle-out.

8 Claims, 3 Drawing Figures r331SECONDARY 0R DAMPING) PAIENIEBJUNZB M5 as I |||||||||||1m rSMSECONDARYOR DAMPING) I11". I!!! M v Q PULSE wwmmsms 4. MP as 55 PULSE WIDTH DR DELAY ims 5m 54 F163 a 25 a .w ss 1 35 DR J L MAIN PULSE 1 CLAMP|NG PULSE L IMPACTING men v \f HAMMER MonoM 0 ims 2ms Ems 4ms 5ms WVENTORS JOHN MAKO MW; CHART JOSEPH EWALLACE ATTORNEY HIGH ENERGY PRINT HAMMER UNIT WITH FAST SETTLE-OUT CROSS-REFERENCE TO RELATED APPLICATION This invention is related to the invention of copending application Ser. No. 156,780 of Joseph E. Wallace and J. Gregory Hamilton, filed June 25, 1971.

FIELD OF INVENTION This invention relates generally to electromagnetic actuators and it has reference in particular to a high energy electromagnetic print hammer.

DESCRIPTION OF PRIOR ART Print hammers have heretofore generally comprised a hammer structure which is actuated by a separate electromagnetic actuator, either directly or through the use of push rods, as in the James M. Cunningham US. Pat. No. 3,241,480, which issued on Mar. 22, 1966.

SUMMARY OF THE INVENTION Generally stated, it is an object of this invention to provide an improved actuator or print hammer.

More specifically, it is an object of this invention to provide a high energy'print hammer which has a reduced settle-out time.

Another object of the invention is to provide a high energy print hammer by improving the efficiency of the electromagnet structure therefor.

Yet another object of the invention is to improve the performance of a print hammer by having only a single moving element.

An important object of the invention is to provide for operating the armature of an electromagnetically operated print hammer so that the principal air gap is always within the operating winding.

Still another object of the invention isto provide a high energy print hammer having a primary magnetic core with an armature movable to impact a document, and a secondary magnetic core with a winding for controlling settle-out.

Another important object of the invention is to provide an electromagnetic print hammer having a magnetic core and an armature, with both primary and secondary magnetic flux operating paths.

Other objects, features and advantages of the invention will be apparent from the following more detailed description of a preferred embodiment of the invention as illustrated in the accompanying drawing.

DESCRIPTION OF THE DRAWING In the drawing: I

FIG. 1 is a partial. schematic view in side elevation of a printer utilizing a magnetically operated print hammer embodying the invention in a preferred form;-

FIG. 2 is a timing diagram; and

FIG. 3 is a schematic block circuit diagram of a control circuit for the primary and secondary operating windings of the print hammer of FIG. 1.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring generally to FIG. 1 of the drawing, the reference numeral designates a high energy print hammer unit which comprises a three-legged magnetic Core Member 12 having an upwardly-curved Upper or Outer Leg 14, a Middle or Center or Outer Leg l6 and a Lower Leg 18. A Primary or Drive Winding 20 is positioned on the Middle Leg 16 and extends beyond the face of the leg. An Armature 22 is pivotally supported adjacent the Lower Leg 18 by a Pivot 24 and one or more upstanding Side Plates 25, which may be part of a Support 13 to which Core Member 12 is secured by Screw l5, and one of which is shown in part. The Armature 22 has a Flag or Projection 26 intermediate its end in alignment with the Middle Leg 16 of the Core Member 12. The Projection 26 is positioned substantially within the Primary or Drive Winding 20 so that the air gap between it and the Middle Leg 16 is completely within the Winding 20. A Spring 23 is positioned within an Opening 21 in the Lower Leg 18 for normally biasing the Armature 22 away from the Middle Leg 16 to the rest position. The Armature 22 has an upwardly-extending Arm Portion 27 provided with a Hammer Face 28 at the upper end for impacting a Ribbon 29 and Document 30 against Type Characters 31, which may be positioned on the surface of a Type Drum, Wheel or other such Type Carrier 32.

In addition to the primary magnetic Core Member 12, a secondary Core Member 33 is provided having an upwardly-curved Leg 34 designed to provide a backstop for the Armature 22, a Middle or Center Leg 35 having a Secondary or Damping Winding 38 positioned thereon, and a Lower Leg portion 36. The secondary Magnet 33 may be pivotally supported on the Piovt 24 by means of a central Projection or Tongue 39 of a Base 42 secured to Core Member 33 by Screws 41. The Tongue 39 fits between spaced Arms 21 of a clevis or the like at the lower end of Armature 22. The Base 42 is provided with an Arm Portion 40 for engagement with adjusting Set Screws 46 and 48 mounted in a slotted Support Member 44. By adjusting the Set Screws 46 and 48 the secondary Core Member 33 may be rotated about the Pivot 24 so as to adjust the rest position of the Armature 22 relative to the primary Core Member 12. The air gap at the Middle Leg 16 of the primary Core may be set to approximately 0.025 inches in the de-energized position, which corresponds to 0.067 inches at the Hammer Face 28. A thin, polyurethane Residual 17 approximately 0.003 inches thick is positioned between the Armature and the main Pole Face 16 and also between the Armature and the secondary Pole Face 38.

In order to print the character, the main Primary or Drive Winding 20 is energized. The Armature 22 is attracted towards the primary Core Member 12 causing the Hammer Face 28 to impact the ribbon and Document 30 against the Type Characters 31. If fast settleout is desired, the Secondary or Clamping Winding 38 is energized about one millisecond after the primary coil is energized, as shown in FIG. 2. Shortly before the Armature 22 seals with the primary Core Member 12, the main pulse is cut off. With the Armature Projection 26 engaging the Residual 17, there is a gap of approximately 0.002 inches between the Arm 27 and the Upper Leg 14. The Hammer 28 continues to move and impacts the Type Characters in about 1.3 milliseconds. During printing the Hammer 28 loses some of its kinetic energy. It rebounds and starts moving back at roughly half the imact velocity. Since the Damping or Secondary Winding 38 is energized as the gap between the secondary Core Member and the Armature narrows, the increasing magnetic force accelerates the returning armature slightly. After impacting the Upper or Support Arm 34 and Residual 37, the Armature 22 would tend to bounce several times. However, since the Secondary or Damping Winding 38 is still energized, the Armature 22 will stay in contact with the Support Arm 34 due to the magnetic force. Therefore, the oscillations set up by the impact force will decay at about 4.2 milliseconds. At this time, the clamping pulse is turned off and the hammer unit is ready for the next operation.

Referring to FIGS. 2 and 3, it will be seen that the Primary or Drive Winding 20 is energized through a Single Shot 50, which provides a pulse width on the order of 1.2 milliseconds and a Driver 52 which provides a peak current on the order of 4.7 amperes. A Diode 53 connected about the Drive Winding 20 minimizes transients. The Secondary or Damping Winding 38 is energized through a current-limiting Resistor 54 and delay means comprising a Single Shot 55 and an Inverter 56. An additional Single Shot 58 provides a pulse width on the order of 3 milliseconds to a Driver 60 which energizes the Secondary Winding 38.

Typical operating characteristics of the high energy print hammer unit are as follows:

Hammer mass 2.46 grams Material 2 /E% silicon iron Kinetic energy 5 200,000 ergs Maximum print force 80-100 pounds Hammer velocity 160 inches/second Contact time 35-70 X seconds Highest repetition rate 5 X 10 seconds Operating voltage 60 volts D.C.

Peak current 4.7 amperes Flight time 1,322 X 10 seconds Hammer motion 0.067 inches From the above description and accompanying drawing it will be apparent that there is provided a high en ergy print hammer unit which has only a single moving part. The subject print hammer unit has a high kinetic energy and it is possible to adjust the magnet so that heavier forms will automatically absorb more of the armatures kinetic energy, so that no impression control is required. An important feature of the design is that the main working gap has been placed inside the operating winding near its center point by use of the projecting flag on the armature. The third arm on the core serves two purposes, (1) to provide mechanical damping of the armature and also (2) to increase the magnetic force by providing an additional working gap. It will be noted however that the Outer Leg 14 has a much smaller cross-section than the Outer Leg 18 so that it has a much higher magnetic reluctance and hence does not detract appreciably from the main operating magnetic flux.

While the invention has been particularly shown and describedwith reference to a preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

The claims are appended hereto:

1. An electromagnetic actuator comprising,

a three-legged core of magnetic material having a middle leg and two outer legs,

an actuator armature-pivotally supported by a pivot at one end adjacent one outer legof said magnetic core and having a projecting intermediate portion spaced from and disposed to move into abutting relation with the middle leg of said yoke,

and an operating winding on said middle leg extending beyond the end of said middle leg to receive said projecting portion of said armature so that said intermediate portion and said middle leg abut within said operating winding and said intermediate portion moves within said winding.

2. The invention as defined in claim 1 characterized by said armature having an extension at the end remote from said pivot support with a print hammer face and being movable on said pivot for impacting a document to print thereon when said intermediate portion and said middle leg abut.

3. The invention as defined in claim 2 characterized by means including an additional core of magnetic material positioned in spaced relation with said threelegged core and on the side of the armature away from said three-legged magnetic core to engage and define the rest position of said armature.

4. The invention'as defined in claim 2 characterized by said one outer leg having a relatively large cross section providing a relatively low reluctance main magnetic flux path with said armature for said operating winding, and said other outer leg extending upwardly to engage said extension portion remote from said projecting armature portion and having a smaller crosssection than said intermediate portion so as to provide a higher reluctance secondary flux path for the mag netic flux produced by said operating winding.

5. The invention as defined in claim 4 characterized by said secondary magnetic core having a control winding thereon.

6. The invention as defined in claim 5 characterized by circuit means including delay means in series with said control winding connected to effect energization of said operating and control windings in predetermined timed relation so that said control winding is energized after said operating winding as said print hammer returns to its rest position.

7. The invention as defined in claim 6 characterized by said secondary magnetic core being pivotally supported by said armature pivot.

8. The invention as defined in claim 5 characterized by said secondary magnetic core having three legs positioned in substantially aligned relation with the legs of said first-mentioned three-legged core and with said armature pivotally mounted to move therebetween.

l l l i l 

1. An electromagnetic actuator comprising, a three-legged core of magnetic material having a middle leg and two outer legs, an actuator armature pivotally supported by a pivot at one end adjacent one outer leg of said magnetic core and having a projecting intermediate portion spaced from and disposed to move into abutting relation with the middle leg of said yoke, and an operating winding on said middle leg extending beyond the end of said middle leg to receive said projecting portion of said armature so that said intermediate portion and said middle leg abut within said operating winding and said intermediate portion moves within said winding.
 2. The invention as defined in claim 1 characterized by said armature having an extension at the end remote from said pivot support with a print hammer face and being movable on said pivot for impacting a document to print thereon when said intermediate portion and said middle leg abut.
 3. The invention as defined in cLaim 2 characterized by means including an additional core of magnetic material positioned in spaced relation with said three-legged core and on the side of the armature away from said three-legged magnetic core to engage and define the rest position of said armature.
 4. The invention as defined in claim 2 characterized by said one outer leg having a relatively large cross section providing a relatively low reluctance main magnetic flux path with said armature for said operating winding, and said other outer leg extending upwardly to engage said extension portion remote from said projecting armature portion and having a smaller cross-section than said intermediate portion so as to provide a higher reluctance secondary flux path for the magnetic flux produced by said operating winding.
 5. The invention as defined in claim 4 characterized by said secondary magnetic core having a control winding thereon.
 6. The invention as defined in claim 5 characterized by circuit means including delay means in series with said control winding connected to effect energization of said operating and control windings in predetermined timed relation so that said control winding is energized after said operating winding as said print hammer returns to its rest position.
 7. The invention as defined in claim 6 characterized by said secondary magnetic core being pivotally supported by said armature pivot.
 8. The invention as defined in claim 5 characterized by said secondary magnetic core having three legs positioned in substantially aligned relation with the legs of said first-mentioned three-legged core and with said armature pivotally mounted to move therebetween. 